In a conventional 3GPP (3rd Generation Partnership Project) system, an eNB has one carrier for each cell, and a UE accesses the one carrier to receive a service. In the conventional 3GPP system, a cell selection process and an RRC (Radio Resource Control) connection setting process of the UE are as follows.
In initial start or a change in a radio environment, the UE searches for the most suitable cell through a cell selection/reselection process, receives system information from an eNB of the searched cell, and camps on the searched cell. Then, when a call is started or a paging process is performed in a network, the UE sets an RRC connection through a random access process.
In the conventional art, an operation for dynamically changing priority based on load by a carrier has not been performed for a UE, RRC connections of which are released, based on load by a carrier. It is necessary to provide a method for efficiently distributing a UE, RRC connections of which are released, on the basis of information representing load on each carrier that is used in a multi-carrier based 3GPP LTE system.